PROJECT SUMMARY/ABSTRACT Childhood cancer survivors are vulnerable to treatment-related late effects, including physical and psychosocial morbidities, subsequent malignancies, and premature death. Symptom assessment provides a unique insight into survivorship care since symptoms not only signal the potential occurrence of chronic health conditions, but also impact quality of life and survival. The National Cancer Institute (NCI) has developed a Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) to assess symptomatic adverse events (AEs) for adult-onset cancer patients who are receiving therapies. However, no evidence supports that the PRO-CTCAE can be used post-therapy for adult survivors of childhood cancer who may experience different symptomatic AEs compared to adult patients undergoing cancer therapies. Our long-term goal for cancer survivorship care is to identify symptomatic AEs for early indication of adverse health events, and design interventions targeting these symptoms for improving health and quality of life outcomes. This proposed study plans to adapt the PRO-CTCAE for use in adult survivors of childhood cancer (PRO-CTCAE-SCC) through three Specific Aims based on unique resources of the Childhood Cancer Survivor Study (CCSS) and the St. Jude Lifetime Cohort Study (SJLIFE): 1) conduct a symptom selection process for the PRO-CTCAE-SCC by identifying symptomatic AEs in adult survivors of childhood cancer, and create items not included in the current PRO-CTCAE; 2) validate the PRO-CTCAE-SCC using psychometric methods and objective clinical parameters; and 3) develop tailored versions of the PRO-CTCAE-SCC for survivors of different diagnoses exposed to different cancer therapies, and establish meaningful cut-points and minimally important differences in symptom burden scores for clinical decision-making. We plan to recruit 135 SJLIFE survivors and 45 healthcare providers who are currently caring for childhood cancer survivors to evaluate content validity. We will recruit 1,200 CCSS survivors to test the psychometric properties of the PRO-CTCAE-SCC, and recruit 600 SJLIFE survivors to evaluate clinical known- groups validity and responsiveness to change. The CCSS and SJLIFE are the two largest, well-established childhood cancer survivor cohorts in North America. In addition, 1,200 age/sex/race matched adults from a community panel will be used to compare the prevalence of symptoms between cancer survivors and non-cancer individuals, leading to a selection of appropriate symptomatic AEs for validation. We will collect chronic health condition, and physical and neurocognitive performance data from the SJLIFE participants following comprehensive medical evaluations to validate the PRO-CTCAE-SCC. Our team includes researchers with expertise in patient-reported outcomes, symptom measurement, neuropsychology, survivorship care, palliative care, and translational science. We have invited six international experts in oncological patient-centered outcomes research and five adult survivors of childhood cancer to serve on the Advisory Committee.